Richard's 620ZX Coupe

[260DET]

lol no more prezzing for me Jason, agree that NatSoft is far better, some events even have live timing. Cheaper as far as entrants go too, MyLaps  transponders are relatively expensive to buy/hire.

[260DET]

Z is back, in the garage and running and driving Needs a bit more work and reassembly, like fitting the engine oil accumulator and making a shift lever console, which I will start on today. Discussed the working of the TCU (transmission control unit) with the tuner who is keen to spend a day at Warwick to do a final tune which he could not do on Brisbane's suburban roads, he does this sort of stuff in his spare time working from his house.

 

The basic setup revolves around the TCC (torque converter clutch) which here is a special heavy duty three plate job, unlike the usual spec relatively light duty single plate type which is typically used only in fourth gear at highway speeds to lock the transmission for fuel economy purposes. Particularly relevant here is the fact that locking the transmission involves bypassing the torque converter by using the TCC in it's place which means that there is no torque converter slip and consequent generated heat from that source. Here the TCU has been set to permanently lock the transmission except in first gear and at a speed less than 50KPH which means that above that speed the top three gears will mechanically transmit engine power just like a manual gearbox does. In contrast first gear will always transmit power through the torque converter, it is anticipated that first will only be used for standing starts. Of course the 50KPH figure can be changed using the TCU if it eventuates that a different speed would be more suitable.

 

So that's the idea, the best characteristics of an auto and a manual all in one. Fingers crossed that in practice it works that way.

[Cozza]

That all sounds pretty good Richard.

Not sure if you have already mentioned but do you know what the gear ratios are.

 

Looking forward to hearing how it all goes in practice.

 

I've always thought a lockable torque converter would suit a ski boat.

 

Mick

[Gordo]

Be nice to have it home Richard . You can do all those little things now. Can't wait for it to hit the track. Cheers.

[260DET]

Gear ratios are stock 4L85E Mick, 2.48, 1.48, 1.00 and .75. With the present 3.9 diff they work out pretty well, keeping in mind the engines broad power band, top speed at a conservative rev limit would be around 250kph which I noticed Sinisha touched a couple of years ago at PI.

 

It's great to have it back Gordo, messing around with a race car is one of my favourite things to do, beats being a spectator that's for sure

[260DET]

Just as well Morgan Park is closed over Xmas because I'm still waiting for the local guru to do a final check of the auto's functions and to do a engine dyno tune. The idea is to get a local bloke involved to do final checks before venturing on to the track, he has a great reputation so like all such tuners has more work than he can handle. I'm not going to risk the equipment when there is an alternative given the bad experience with the VG30DET donk.

 

In the meantime a new dual element rear wing has been set up and fitted, see pic below which is a bit deceptive, the wing is not as wide as it looks. Rather than have a wide single the idea was to have a narrower dual so it would be operating within the wake of the car which should result in the optimum angle being consistent across the width. Not sure about drag but the idea is to have less anyway. 

 

The other job now completed is new cabin air extractor vents in the quarter windows and a sliding window in the driver's door. That window was located as far back as possible to avoid any debris which may enter from hitting me in the face. Yes that did happen once with the original window wound right down.

 

 

[gav240z]

It's great to have it back Gordo, messing around with a race car is one of my favourite things to do, beats being a spectator that's for sure

 

You obviously don't know how to be an arm chair spectator, it's great fun. You can tell people how to drive better, complain about their cornering technique, tell them why their car sucks and generally be a nuisance without putting any of your own skin in the game or taking any risks. It's great fun!

[260DET]

Yes Gavin, I have struck the occasional person who is full of, err, 'good advice' Back to the project.

 

This is how projects that try something different can chew up time. To  summarise so far, I decided to put a sequential shift auto behind the LS3 which I still think is a good idea for me. The Z is all together and is a runner but needed a dyno tune and a final check that the auto was working the way it should. Guru puts it on the dyno and around 5000 revs the engine surges which indicates that the lock up clutch is slipping. Shuts it all down and we discuss it and particularly the torque converter. To get it on the track if only temporary I agree that the lock up clutch should be disabled and dyno testing proceed to see if the converter will hold the power without excessive slipping. That's where it is now.

 

After doing some research I've decided to look at the sort of converter used in US circle track racing but there is nothing off the shelf to suit my 4L85E transmission. The circle track converters are designed to be 'tight', not much slip, very efficient at racing revs and relatively low stall. The more efficient the less wasted power and consequential heat which is very important. I've emailed TCI in the US to see what they can do so that's where the project is now. Sigh.

[PB260Z]

Yes Gavin, I have struck the occasional person who is full of, err, 'good advice' Back to the project.

[260DET]

Just to make it clear, the original idea was to have the lock up clutch permanently on in 2,3 and 4th gears. This was to eliminate the slipping effect of your usual converter, more power to the ground and consequentially less heat. Now the idea is to eventually delete the lock up clutch requirement, which would save weight too, and use a super efficient converter that would operate 100% of the time.

 

The thing is, is something like that available in this country where high performance torque converters are invariably set up for drag racing.

[260DET]

It's official, the torque converter's clutch is slipping and so will be useless for track purposes. Otherwise the TC does not seem to be ideal for a circuit car but guru and I agree that once a few final tweeks have been done it would be best to test the Z around MP to see how it goes, one good thing he has found is that the transmission is running relatively cool which indicates it must be fairly efficient. I'm really annoyed though, bloody car component suppliers who take your money and do a crap job.

 

The thing is that converters to suit are built in the US with up to four plate clutches that will take 1000 hp and wide open throttle shifts so I wasn't asking for something that could not be done. It looks like a more suitable clutchless TC will be required, if so it will be coming from the US no matter how much it costs.

[Gordo]

That's a bummer Richard, bit of a set back time wise.

[260DET]

Luckily there is a local bloke, 'the guru', who does dyno tuning and general performance car work who has been able to work through the problems and also tweak the transmission control unit to shift faster. So that's good, he is a drag racer who has had some experience with his own auto so he has some idea what is required. There are plenty of people around who will sell you something but very few capable of sorting through problems resulting from their mistakes so I'm lucky there.

 

Looking forward to going for a run, I'm sure that once sorted the Z is going to be hella fun to drive

[dat2kman]

Excellent!

Do a Wednesday Mrg Park test day, jst to iron ut the bugs!

[260DET]

Woohoo, I think, got the car back today so the next move is to track test it. After hooking up the Accusump system and tidying a few things up plus getting a front strut/firewall brace made after I weld in some attachment points. 

 

The guru has sorted a few things out including getting the lockup clutch to hold, it wasn't due to an incorrect setting. Anyway we agree that the car needs a track test because there are quite a few things to test so after that the guru will make any further adjustments required. With features like full throttle shifts the system has to be properly tuned so that it all comes together on the track which, hopefully, will be on the 25th at MP.

[zed74]

good news

[260DET]

Yep, looks like the 25th is the go, for once whatever has to be done to get the Z track worthy is on schedule. Any other Zeds going to be there?

[260DET]

Report from the Morgan Park practice. The good includes that the Z actually goes and after two years abstinence the senior driver thinks that he can still turn a wheel. Torque converter which we thought was rubbish seems pretty good, great throttle response and overall powers. New brake pads have lots of bite, way better than anything else I've tried.

 

The bad? Sequential shift was not working at all, it had been on the dyno, so I just drove around in auto pretending to be a race driver. Guru says to get the back wheels up off the ground and try running it through the gears sequentially and then get back to him.

[260DET]

Being a bugger for punishment it's back to MP tomorrow for 'more practice'. The guru did some more tweaking today but there is still a problem with sequential downshifts, we agree that a gear indicator is essential as it is for all sequential shifts so he is going to look at that. The plan is to use full auto for a while tomorrow to get used to the powertrain and then try sequential later.

[Gordo]

Go to hear your out on the track Richard . Now you have to re program the brain to the new car.

[Mike260LW]

That's good news Richard! Unfortunately MP Super Sprint Rd 2, is a fair way off. First weekend of May I think. Still, plenty of practice days to fine tune and hone skills.

[260DET]

Another hohum day as far as the auto goes although I got up it a bit more this time and came close to scaring myself which is when the fun is best New brake pads are working well, the big front discs are now blue for the first time ever, used to use A1RM's and Lucas which have nowhere near the bite.

 

The only place to sort this auto out is at the track, dyno and road runs are pretty useless, that should happen on the next practice day. There is absolutely no info of any use around on what we are doing, maybe there is a good reason for that lol.

[260DET]

For anyone interested in the auto setup. 

 

Been querying the bloke who originally set the TCU up and have come up with two points of interest. Firstly he set a 0.5 second ignition cut during upshifts which seems to be a good idea and apparently is common with the latest euro sports autos although I'm thinking 0.3 may be a better starting point? Might add that when driving the car I was unaware that there was an ignition cut which is good but perhaps 0.3 will make for a snappier shift, we will see. To explain how the cut works, the TCU (transmission control unit) tells the ECU when and for how long, cool eh.

 

Secondly, this is a bit more complicated in practice but the principle is simple. He set the TCU up to block (accidental) downshifts made at excessive revs, good idea. But he thinks that the way it was done may be interfering with normal downshifts given that on the track downshifts made at fairly low revs often did not happen immediately which of course is not a good thing. But now we know about this it can be looked at and sorted. Downshifts are tricky because of rev mismatching and the need for them to happen quickly so basically they should be made at low revs and certainly not used as part of a engine braking driving style.

[PeterAllen]

Luckily I was born with a brain, and gross and fine motor skills, so I can do all that stuff already!

 

To each his own and I'm probably old fashioned but, I like to see more driver input, not less.

[260DET]

We could get really physical Peter and go back to walking, concerning the brain well there is plenty involved in setting this auto up I can tell you. As far as race driving goes all having a clutchless sequential shift transmission does is free a bit of the brain up from doing mundane things like manually pushing gears around. Some people like doing that, I don't and would rather use my limited abilities to manage the car better on the track. For me nothing beats the (rare) moment where the car is going faster than it should but is still nicely balanced, playing with a gear lever has nothing on that.